Not Applicable
This invention relates to a printhead chip for an inkjet printhead. More particularly, this invention relates to a printhead chip for an inkjet printhead that incorporates pusher actuation in order to achieve ink drop ejection.
As set out in the above referenced applications/patents, the Applicant has spent a substantial amount of time and effort in developing printheads that incorporate micro electro-mechanical system (MEMS)xe2x80x94based components to achieve the ejection of ink necessary for printing.
As a result of the Applicant""s research and development, the Applicant has been able to develop printheads having one or more printhead chips that together incorporate up to 84 000 nozzle arrangements. The Applicant has also developed suitable processor technology that is capable of controlling operation of such printheads. In particular, the processor technology and the printheads are capable of cooperating to generate resolutions of 1600 dpi and higher in some cases. Examples of suitable processor technology are provided in the above referenced patent applications/patents.
Common to most of the printhead chips that the Applicant has developed is a component that moves with respect to a substrate to eject ink from a nozzle chamber. This component can be in the form of an ink-ejecting member that is displaceable in a nozzle chamber to eject the ink from the nozzle chamber.
As is also clear from the above applications, Applicant has developed a number of ways in which to achieve the ejection of ink from the respective nozzle chambers. A majority of these are based on the selection of a material having a coefficient of thermal expansion that is such that, on a MEMS scale, expansion upon heating and subsequent contraction upon cooling can be harnessed to perform work. The material is formed to define at least part of a thermal actuator that includes a heating circuit. The heating circuit is shaped to be resistively heated when a current passes through the circuit. The current is supplied to the circuit in the form of pulses at a frequency that depends on the printing requirements. The pulses are usually supplied from a CMOS layer positioned on a substrate of the printhead chip. The pulses are shaped and have a magnitude that is also dependent on the printing requirements. The generation and control of the pulses is by way of a suitable microprocessor of the type described in the above referenced applications.
On a macroscopic scale, it is counter-intuitive to use the expansion and subsequent contraction of material in order to achieve the performance of work. Applicant submits that the perceived slow rate of expansion and contraction would lead a person of ordinary skill in the field of macroscopic engineering to seek alternative energy sources.
On a MEMS scale, however, Applicant has found that expansion and contraction of such a material can be harnessed to perform work. The reason for this is that, on this scale, expansion and contraction are relatively rapid and can transmit relatively high force.
There remains an issue of range of movement. While the expansion and contraction are both rapid and forceful, Applicant has found that it would be desirable for a mechanism to be provided whereby such rapidity and force of movement could be amplified at a region where the work is required to eject the ink.
A majority of the nozzle arrangements covered by the above applications and patents use differential expansion in the thermal actuator to achieve bending of the thermal actuator. This bending movement is transmitted to an ink-ejecting component that is either rectilinearly or angularly displaced to eject the ink.
Applicant has found that it would be desirable for simple rectilinear expansion of a thermal actuator to be transmitted to an ink-ejecting component, since such simple rectilinear expansion on a MEMS scale is relatively efficient.
The Applicant has conceived this invention in order to achieve the desired transmission and amplification of motion mentioned above.
According to the invention, there is provided a printhead chip for an inkjet printhead, the printhead chip comprising
a substrate; and
a plurality of nozzle arrangements that is positioned on the substrate, each nozzle arrangement comprising
a nozzle chamber structure that is positioned on the substrate and that defines a nozzle chamber from which ink is to be ejected;
an ink-ejecting mechanism that is operatively arranged with respect to the nozzle chamber structure, the ink-ejecting mechanism including at least one moving component that is displaceable to generate a pressure pulse within the nozzle chamber to eject ink from the nozzle chamber;
an actuator that is positioned on the substrate and that has at least one working member that is of a material having a coefficient of thermal expansion such that the, or each, working member is capable of substantially rectilinear expansion and contraction when heated and subsequently cooled; and
an energy transmitting means that interconnects the, or each, moving component and the, or each, working member so that energy generated by the, or each, working member as a result of expansion and subsequent contraction of the, or each, working member is transmitted to the, or each, moving component resulting in displacement of the, or each, moving component and generation of said pressure pulse.
The invention is now described, by way of examples, with reference to the accompanying drawings. The following description is not intended to limit the broad scope of the above summary.